Make the front panel compile again, submitted by Duncan Coutts
<duncan.coutts@worc.ox.ac.uk>.  From his email:

Attached is a patch to port the GHC RTS font panel to Gtk+ 2.x rather
than the obsolete Gtk+ 1.2.

There were basically two changes needed. Change the configure check to
look for the pkg-config utility rather than the old gtk-config. At it's
just checking for Gtk+ 2.0 or later. It may be that the new code
actually needs a slightly later version than that. I'm not quite sure.

The other change was to convert the ghc-fontpanel.glade file to the
glade-2 format using the libglade-convert script and then to re-generate
the C code for constructing the GUI, that is the Vis*.c Vis*.h files in
ghc/rts.

The front panel has been bit-rotting for quite some time so it has not
kept up with changes in the rts structures. So I had to comment out
references to 3 bits that no longer exist. I've left FIXMEs in the code
at the appropriate places so that someone wiser than me can make the
appropriate changes.

So the thing does now build though I have no doubt that it will not run,
or at least will not do the right thing because it has not yet been
updated to the current state of the rts. However hopefully now that it
is at least buildable with a modern Gtk+ version someone else might be
able to fix it up.

This also relates to trac ticket #599:

http://cvs.haskell.org/trac/ghc/ticket/599